Progressing cavity pumps are used in various applications, including downhole oilfield applications to pump fluids to the surface. Progressing cavity downhole motors are similar tools commonly used to convert hydraulic energy into mechanical energy, e.g., to rotate a drill bit. The interior surface of the stator is typically formed from an elastomeric material which acts as a contact seal with the rotor. The contact areas determine the perimeter of the cavities which contain the working fluid, and these cavities progress from one end of the pump/motor to the other end of the pump/motor during its operation.
In certain applications, the operational temperature range intended for the pump/motor exceeds the practical maximum temperature of elastomeric materials or the corresponding adhesive. Materials, both elastomeric and rigid, have been used for both the surface of the rotor and the stator subjected to these conditions. For rigid material applications, a clearance between the rotor and the stator replaces the contact seal between the two parts formed in other applications when using an elastomeric seal. The clearance between the rotor and stator is either designed, or worn into the rotor and/or stator during operation. Such a design can significantly reduce the efficiency due to the volume of the working fluid passed between the I.D. of the stator and the O.D. of the rotor. Such pump/motor designs are not favored in most applications because of their poor efficiency.
Progressing cavity pump/motors are disclosed in U.S. Pat. Nos. 6,120,267, 6,491,501, 6,695,060, 7,214,042, 7,407,372, 7,553,139, and Publications US 2010/0316518 and US 2010/0322808. Such pumps conventionally contain an elastomeric layer on the inner surface of the stator for deforming during rotation of the rotor to form a contact seal. U.S. Pat. No. 7,837,451 discloses a rotor with lobes and grooves in the casing for use in pulse detonation combustors (PDC's) and engines (PDE's). Grooves are provided on a tip portion of the lobes and presumably increase air pressure to the combustion chamber. Pumps and motors according to the present invention rely upon a working fluid, which conventionally is a mixture of liquids, solids, and often some gas, to generate energy or to transfer fluids.
The disadvantages of the prior art are overcome by the present invention, an improved pump/motor is hereinafter disclosed.